Sarmatimactra fabreana (d’Оrbigny, 1844)

Frolov, Pavel D., Danukalova, Guzel A. & Osipova, Eugenia M., 2018, Late Miocene molluscs of the Morskaya 2 site (Azov Sea region, Russia), Palaeontologia Electronica (a 20) 23 (1), pp. 1-32 : 21

Sarmatimactra fabreana (d’Оrbigny, 1844)

Figure 3.5-6

1844 Mactra ponderosa (on the plate Fabreana) d’Оrbigny, p. 479, pl. 27, figs. 1-6.

1935 Mactra fabreana d’Оrbigny ; Kolesnikov, p.

50, pl. 5, figs. 1-4.

1969 Mactra (Sarmatimactra) vitaliana fabreana d’Оrbigny ; Kojumdgieva, p. 22, pl. 5, figs.

2-3.

1976 Mactra (Sarmatimactra) fabreana d’Оrbigny ; Iljina, Nevesskaya, and Paramonova, pl. 9, figs. 4-9.

1993 Mactra (Sarmatimactra) fabreana d’Оrbigny ; Nevesskaya, Goncharova, Paramonova, Popov, Babak, Bagdasaryan, and Voronina, p. 295, pl. 70, figs. 3-6.

Material. 3 specimens from layer 1 (3 left valves, 2 right valves) and 1 specimen from layer 3 (1 left valve, 1 right valve, 108 fragments).

Description. Rounded-triangular shell (all the valves of our collection are broken off along the length) (HS up to 46 mm; Con. up to 18 mm), large, thick-walled, equivalve. Closure of the valves is dense. Umbo is high, convex, blunt, turned forward. The anterior branch of the hinge edge is inclined and gradually merges into a rounded anterior edge. The posterior branch of the hinge edge is also smoothly inclined and merges smoothly into an angular, slightly abducted posterior edge. The ventral edge is convex. Valves slightly inequilateral, convex. There is a clear rounded keel from the umbo to the posterior lower corner of the valve. Posterior slope is covered by very coarse growth lines, on the other part of shell they are less coarse, thinning when approaching the umbo.

Hinge area is wide and arcuated. Hinge is massive. The right valve it consists of one lambdoid-shaped cardinal tooth and two pairs of lateral teeth. There is a spoon-shaped concavity of the internal ligament between the posterior lateral and cardinal teeth, above which there is a small depression of the outer ligament, separated by a thin plate. There is one lambdoid-shaped cardinal and a pair of single oval-round lateral teeth in the left valve. The cardinal tooth and the concavity of the internal ligament are separated by a thin plate. The inner surface of the shell with a pallial line, sinus is rounded, shallow. The scars of the anterior and posterior muscles are clear, oval. There are visible scars of mantle muscles of irregularly rounded shape above the mantle line.

Remarks. Sarmatimactra is considered a genus distinct from Mactra (Sepkoski, 2002) .

Region of distribution and age. The beginning of Late Miocene of Southern and Eastern Europe, Ciscaucasia, Transcaucasia, Mangyshlak, Turkmenia (Nevesskaya et al., 1993).

Figures

FIGURE 3. Assemblage of the Middle Sarmatian (Bessarabian) marine bivalves (layer 1). 1-2, Polititapes ponderosa (d’Orbigny, 1844). 3-4, Polititapes vitaliana (d’Orbigny, 1844). 5-6, Sarmatimactra fabreana (d’Оrbigny, 1844). 7-8, Obsoletiformes obsoletum ingratum (Kolesnikov, 1929). 9-10, Obsoletiformes obsoletum obsoletum (Eichwald, 1830). 11, Plicatiforma fittoni fittoni (d’Orbigny in Murchison et al., 1845). 12-13, Ervilia dissita dissita (Eichwald, 1830).

FIGURE 4. Assemblage of the Middle Sarmatian (Bessarabian) marine gastropods (layers 1 and 2). 1, Acteocina lajonkaireana (Basterot, 1825). 2, Acteocina okeni (Eichwald, 1850). 3, Retusa melitopolitana (Sokolov, 1899). 4, Hydrobia elongata Eichwald, 1830. 5, Pseudamnicola nympha (Eichwald, 1850). 6, Dorsanum duplicata opinabile (Kolesnikov, 1932). 7, Dorsanum corbiana (d’Orbigny, 1844). 8, Dorsanum ignobile (Kolesnikov, 1932). 9, Gibbula (Gibbula) pseudoangulata (Sinzov, 1875). 10, Gibbula (Sarmatigibbula) podolica (Du Bois de Montpéreux, 1831).

FIGURE 5. Assemblage of the Maeotian freshwater molluscs (layer 3). 1, Borysthenia cf. pronaticina (Lindholm, 1932). 2-3, Lithoglyphus acutus Cobălcescu, 1883; 2, smooth shell; 3, shell with keel. 4, Viviparus cf. karaganicus Volkova, 1939. 5, Viviparus cf. maeoticus (Bogachev and Shishkina, 1919). 6, Lymnaea sp. 7, Sphaerium rivicola Lamarck, 1818. 8, Gyraulus cf. acronicus (Ferrussac, 1807). 9-10, Bithyniidae, opercula.

FIGURE 6. Assemblage of the Maeotian terrestrial molluscs (layer 3). 1, cf. Helicella sp. 2, Helicodiscus (Helicodis- cus) roemeri (Andreae, 1902). 3, Vallonia cf. pulchella (Müller, 1774). 4-5,? Deroceras sp.